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Four-fold channels are involved in iron diffusion into the inner cavity of plant ferritin.

Biochemistry (2014-04-01)
Chenyan Lv, Shengli Zhang, Jiachen Zang, Guanghua Zhao, Chuanshan Xu
ABSTRACT

From an evolutionary point of view, plant and animal ferritins arose from a common ancestor, but plant ferritin exhibits different features as compared with the animal analogue. One major difference is that the 4-fold channels naturally occurring in plant ferritin are hydrophilic, whereas the 4-fold channels in animal ferritin are hydrophobic. Prior to this study, however, the function of the 4-fold channels in oxidative deposition of iron in phytoferritin remained unknown. To elucidate the role of the 4-fold channels in iron oxidative deposition in ferritin, three mutants of recombinant soybean seed H-2 ferritin (rH-2) were prepared by site-directed mutagenesis, which contained H193A/H197A, a 4-fold channel mutant, E165I/E167A/E171A, a 3-fold channel mutant, and E165I/E167A/E171A/H193A/H197A, where both 3- and 4-channels were mutated. Stopped-flow, electrode oximetry, and transmission electron microscopy (TEM) results showed that H193A/H197A and E165I/E167A/E171A exhibited a similar catalyzing activity of iron oxidation with each other, but a pronounced low activity compared to rH-2, demonstrating that both the 4-fold and 3-fold hydrophilic channels are necessary for iron diffusion in ferritin, followed by oxidation. Indeed, among all tested ferritin, the catalyzing activity of E165I/E167A/E171A/H193A/H197A was weakest because its 3- and 4- fold channels were blocked. These findings advance our understanding of the function of 4-fold channels of plant ferritin and the relationship of the structure and function of ferritin.

MATERIALS
Product Number
Brand
Product Description

Sigma-Aldrich
Carbonyl iron, ≥97% Fe basis
Sigma-Aldrich
Ferritin from human liver, Type IV, 10 μg/mL
Sigma-Aldrich
Iron, foil, thickness 0.25 mm, ≥99.99% trace metals basis
Sigma-Aldrich
Iron, granular, 10-40 mesh, >99.99% trace metals basis
Sigma-Aldrich
Iron, powder, <10 μm, ≥99.9% trace metals basis
Sigma-Aldrich
Iron, wire, diam. 1.0 mm, ≥99.9% trace metals basis
Sigma-Aldrich
Iron, ≥99%, reduced, powder (fine)
Sigma-Aldrich
Iron, wire, diam. 1.0 mm, ≥99.99% trace metals basis
Iron, foil, light tested, 25x25mm, thickness 0.01mm, 99.99+%
Iron, foil, 6mm disks, thickness 0.009mm, 99.85%
Iron, foil, 8mm disks, thickness 0.025mm, as rolled, 99.99+%
Iron, foil, 50mm disks, thickness 0.125mm, hard, 99.5%
Iron, foil, light tested, 25x25mm, thickness 0.025mm, as rolled, 99.99+%
Iron, foil, 5m coil, thickness 0.038mm, hard, 99.5%
Iron, foil, not light tested, 100x100mm, thickness 0.015mm, 99.85%
Iron, foil, 8mm disks, thickness 0.005mm, 99.85%
Iron, foil, 8mm disks, thickness 1.0mm, as rolled, 99.5%
Iron, foil, 6mm disks, thickness 0.003mm, 99.85%
Iron, foil, light tested, 50x50mm, thickness 0.075mm, hard, 99.5%
Iron, foil, 8mm disks, thickness 0.0125mm, 99.85%
Iron, foil, 8mm disks, thickness 0.125mm, as rolled, 99.99+%
Iron, foil, 5m coil, thickness 0.025mm, hard, 99.5%
Iron, foil, 6mm disks, thickness 0.015mm, 99.85%
Iron, foil, not light tested, 100x100mm, thickness 0.0125mm, 99.99+%
Iron, foil, light tested, 150x150mm, thickness 0.05mm, hard, 99.5%
Iron, foil, 8mm disks, thickness 0.9mm, as rolled, 99.5%
Iron, foil, light tested, 25x25mm, thickness 0.01mm, 99.85%
Iron, foil, light tested, 50x50mm, thickness 0.075mm, as rolled, 99.99+%
Iron, foil, 6mm disks, thickness 0.075mm, as rolled, 99.99+%
Iron, foil, 6mm disks, thickness 0.006mm, 99.85%